Optical imaging lens

ABSTRACT

An optical imaging lens includes a first lens element to a sixth lens element. The first lens element has positive refracting power, an optical axis region of the object-side surface of the second lens element is convex, the third lens element has positive refracting power and an optical axis region of the image-side surface of the third lens element is convex, and an optical axis region of the image-side surface of the fifth lens element is convex. ImgH is an image height of the optical imaging lens, Fno is the f-number of the optical imaging lens, υ2, υ3, υ4 and υ6 are respectively an Abbe number of the second, the third, the fourth and the sixth lens element to satisfy ImgH/Fno≥2.000 mm and υ2+υ3+υ4+υ6≤135.000.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to an optical imaging lens. Specifically speaking, the present invention is directed to an optical imaging lens for use in such as a mobile phone, a camera, a tablet personal computer, or a personal digital assistant (PDA) and for a picture-taking device for use in cars for taking pictures or for recording videos.

2. Description of the Prior Art

In recent years, an optical imaging lens improves along with its wider and wider applications. In addition to being lighter, thinner, shorter and smaller, a design with a smaller F-number (Fno) facilitates the increase of the luminous flux. Besides, a larger field of view is becoming a trend of the market. In addition, in order to increase pixels and improve resolution, it is necessary to increase the image height of the lens, by using a larger image sensor to receive imaging light to meet the requirement of more pixels.

Accordingly, it is always a target of the design in the art to come up with a lighter, thinner, shorter and smaller optical imaging lens with a smaller F-number, with a larger field of view, with greater image height and with good imaging quality at the same time to solve the problems.

SUMMARY OF THE INVENTION

In the light of the above, various embodiments of the present invention propose an optical imaging lens of six lens elements which has reduced system length, ensured imaging quality, a smaller F-number, a larger field of view, greater image height, good optical performance and is technically possible. The optical imaging lens of six lens elements of the present invention from an object side to an image side in order along an optical axis has a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. Each first lens element, second lens element, third lens element, fourth lens element, fifth lens element and sixth lens element respectively has an object-side surface which faces toward the object side and allows imaging rays to pass through as well as an image-side surface which faces toward the image side and allows the imaging rays to pass through.

In one embodiment, the first lens element has positive refracting power, an optical axis region of the object-side surface of the second lens element is convex, the third lens element has positive refracting power and an optical axis region of the image-side surface of the third lens element is convex, and an optical axis region of the image-side surface of the fifth lens element is convex. The optical imaging lens has only six lens elements to satisfy the relationship: ImgH/Fno≥2.000 mm and υ2+υ3+υ4+υ6≤135.000.

In another embodiment, an optical axis region of the object-side surface of the second lens element is convex, an optical axis region of the object-side surface of the third lens element is concave; the fourth lens element has negative refracting power, an optical axis region of the object-side surface of the fifth lens element is concave, and an optical axis region of the object-side surface of the sixth lens element is concave. The optical imaging lens has only six lens elements to satisfy the relationship: ImgH/Fno≥2.000 mm and (EFL+ImgH)/(Tmax+Gmax)≥6.000.

In still another embodiment, an optical axis region of the object-side surface of the second lens element is convex, an optical axis region of the object-side surface of the third lens element is concave, the fourth lens element has negative refracting power, an optical axis region of the object-side surface of the fifth lens element is concave, and an optical axis region of the object-side surface of the sixth lens element is concave and a periphery region of the image-side surface of the sixth lens element is convex. The optical imaging lens has only six lens elements to satisfy the relationship: ImgH/Fno≥2.000 mm and (EFL+ImgH)/(Gmax+Gmax2)≥9.300.

In the optical imaging lens of the present invention, the embodiments may also selectively satisfy the following optical conditions:

-   1. TTL/(G12+G34)≤16.500; -   2. (T1+T2+T3)/(G12+G34)≤5.200; -   3. AAG/(G34+T4)≤3.000; -   4. (T4+BFL)/(G23+T3+G56)≥1.400; -   5. T1/T5≤1.000; -   6. (T2+G23+G45)/T3≥2.700; -   7. TTL/(G12+T3)≥11.000; -   8. (T4+T6)/G45≤2.200; -   9. ALT/(G34+T5)≤3.000; -   10. (T1+T5+BFL)/AAG≥1.700; -   11. TL/(T3+T4)≥6.000; -   12. (G12+T2+T5)/(T3+T6)≥1.100; -   13. TTL/T6≥10.500; -   14. (T1+T4)/G56≥2.100; -   15. ALT/(G23+T3+G56)≥3.000; -   16. ImgH/AAG≥2.600; -   17. TL/(G45+G56)≥5.000.

In order to facilitate clearness of the parameters represented by the present invention and the drawings, it is defined in this specification and the drawings: T1 is a thickness of the first lens element along the optical axis; T2 is a thickness of the second lens element along the optical axis; T3 is a thickness of the third lens element along the optical axis; T4 is a thickness of the fourth lens element along the optical axis; T5 is a thickness of the fifth lens element along the optical axis; and T6 is a thickness of the sixth lens element along the optical axis. G12 is an air gap between the first lens element and the second lens element along the optical axis; G23 is an air gap between the second lens element and the third lens element along the optical axis; G34 is an air gap between the third lens element and the fourth lens element along the optical axis; G45 is an air gap between the fourth lens element and the fifth lens element along the optical axis; G56 is an air gap between the fifth lens element and the sixth lens element along the optical axis. Tmax is the largest thickness of a lens element from the first lens element to the sixth lens element, Gmax is the largest air gap from the first lens element to the sixth lens element, and Gmax2 is the second largest air gap from the first lens element to the sixth lens element.

ALT is a sum of thicknesses of all the six lens elements along the optical axis. AAG is a sum of five air gaps from the first lens element to the sixth lens element along the optical axis. In addition, TTL is a distance from the object-side surface of the first lens element to an image plane along the optical axis, and that is the system length of the optical imaging lens; EFL is an effective focal length of the optical imaging lens; TL is a distance from the object-side surface of the first lens element to the image-side surface of the sixth lens element along the optical axis. BFL is a distance from the image-side surface of the sixth lens element to the image plane along the optical axis. Fno is the f-number of the entire optical imaging lens. HFOV is the half field of view of the entire optical imaging lens. ImgH is an image height of the optical imaging lens. υ2 is an Abbe number of the second lens element, υ3 is an Abbe number of the third lens element, υ4 is an Abbe number of the fourth lens element and υ6 is an Abbe number of the sixth lens element.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrate the methods for determining the surface shapes and for determining an optical axis region and a periphery region of one lens element.

FIG. 6 illustrates a first embodiment of the optical imaging lens of the present invention.

FIG. 7A illustrates the longitudinal spherical aberration on the image plane of the first embodiment.

FIG. 7B illustrates the field curvature aberration on the sagittal direction of the first embodiment.

FIG. 7C illustrates the field curvature aberration on the tangential direction of the first embodiment.

FIG. 7D illustrates the distortion aberration of the first embodiment.

FIG. 8 illustrates a second embodiment of the optical imaging lens of the present invention.

FIG. 9A illustrates the longitudinal spherical aberration on the image plane of the second embodiment.

FIG. 9B illustrates the field curvature aberration on the sagittal direction of the second embodiment.

FIG. 9C illustrates the field curvature aberration on the tangential direction of the second embodiment.

FIG. 9D illustrates the distortion aberration of the second embodiment.

FIG. 10 illustrates a third embodiment of the optical imaging lens of the present invention.

FIG. 11A illustrates the longitudinal spherical aberration on the image plane of the third embodiment.

FIG. 11B illustrates the field curvature aberration on the sagittal direction of the third embodiment.

FIG. 11C illustrates the field curvature aberration on the tangential direction of the third embodiment.

FIG. 11D illustrates the distortion aberration of the third embodiment.

FIG. 12 illustrates a fourth embodiment of the optical imaging lens of the present invention.

FIG. 13A illustrates the longitudinal spherical aberration on the image plane of the fourth embodiment.

FIG. 13B illustrates the field curvature aberration on the sagittal direction of the fourth embodiment.

FIG. 13C illustrates the field curvature aberration on the tangential direction of the fourth embodiment.

FIG. 13D illustrates the distortion aberration of the fourth embodiment.

FIG. 14 illustrates a fifth embodiment of the optical imaging lens of the present invention.

FIG. 15A illustrates the longitudinal spherical aberration on the image plane of the fifth embodiment.

FIG. 15B illustrates the field curvature aberration on the sagittal direction of the fifth embodiment.

FIG. 15C illustrates the field curvature aberration on the tangential direction of the fifth embodiment.

FIG. 15D illustrates the distortion aberration of the fifth embodiment.

FIG. 16 illustrates a sixth embodiment of the optical imaging lens of the present invention.

FIG. 17A illustrates the longitudinal spherical aberration on the image plane of the sixth embodiment.

FIG. 17B illustrates the field curvature aberration on the sagittal direction of the sixth embodiment.

FIG. 17C illustrates the field curvature aberration on the tangential direction of the sixth embodiment.

FIG. 17D illustrates the distortion aberration of the sixth embodiment.

FIG. 18 illustrates a seventh embodiment of the optical imaging lens of the present invention.

FIG. 19A illustrates the longitudinal spherical aberration on the image plane of the seventh embodiment.

FIG. 19B illustrates the field curvature aberration on the sagittal direction of the seventh embodiment.

FIG. 19C illustrates the field curvature aberration on the tangential direction of the seventh embodiment.

FIG. 19D illustrates the distortion aberration of the seventh embodiment.

FIG. 20 illustrates an eighth embodiment of the optical imaging lens of the present invention.

FIG. 21A illustrates the longitudinal spherical aberration on the image plane of the eighth embodiment.

FIG. 21B illustrates the field curvature aberration on the sagittal direction of the eighth embodiment.

FIG. 21C illustrates the field curvature aberration on the tangential direction of the eighth embodiment.

FIG. 21D illustrates the distortion aberration of the eighth embodiment.

FIG. 22 shows the optical data of the first embodiment of the optical imaging lens.

FIG. 23 shows the aspheric surface data of the first embodiment.

FIG. 24 shows the optical data of the second embodiment of the optical imaging lens.

FIG. 25 shows the aspheric surface data of the second embodiment.

FIG. 26 shows the optical data of the third embodiment of the optical imaging lens.

FIG. 27 shows the aspheric surface data of the third embodiment.

FIG. 28 shows the optical data of the fourth embodiment of the optical imaging lens.

FIG. 29 shows the aspheric surface data of the fourth embodiment.

FIG. 30 shows the optical data of the fifth embodiment of the optical imaging lens.

FIG. 31 shows the aspheric surface data of the fifth embodiment.

FIG. 32 shows the optical data of the sixth embodiment of the optical imaging lens.

FIG. 33 shows the aspheric surface data of the sixth embodiment.

FIG. 34 shows the optical data of the seventh embodiment of the optical imaging lens.

FIG. 35 shows the aspheric surface data of the seventh embodiment.

FIG. 36 shows the optical data of the eighth embodiment of the optical imaging lens.

FIG. 37 shows the aspheric surface data of the eighth embodiment.

FIG. 38 shows some important parameters in the embodiments.

FIG. 39 shows some important ratios in the embodiments.

DETAILED DESCRIPTION

The terms “optical axis region”, “periphery region”, “concave”, and “convex” used in this specification and claims should be interpreted based on the definition listed in the specification by the principle of lexicographer.

In the present disclosure, the optical system may comprise at least one lens element to receive imaging rays that are incident on the optical system over a set of angles ranging from parallel to an optical axis to a half field of view (HFOV) angle with respect to the optical axis. The imaging rays pass through the optical system to produce an image on an image plane. The term “a lens element having positive refracting power (or negative refracting power)” means that the paraxial refracting power of the lens element in Gaussian optics is positive (or negative). The term “an object-side (or image-side) surface of a lens element” refers to a specific region of that surface of the lens element at which imaging rays can pass through that specific region. Imaging rays include at least two types of rays: a chief ray Lc and a marginal ray Lm (as shown in FIG. 1). An object-side (or image-side) surface of a lens element can be characterized as having several regions, including an optical axis region, a periphery region, and, in some cases, one or more intermediate regions, as discussed more fully below.

FIG. 1 is a radial cross-sectional view of a lens element 100. Two referential points for the surfaces of the lens element 100 can be defined: a central point, and a transition point. The central point of a surface of a lens element is a point of intersection of that surface and the optical axis I. As illustrated in FIG. 1, a first central point CP1 may be present on the object-side surface 110 of lens element 100 and a second central point CP2 may be present on the image-side surface 120 of the lens element 100. The transition point is a point on a surface of a lens element, at which the line tangent to that point is perpendicular to the optical axis I. The optical boundary OB of a surface of the lens element is defined as a point at which the radially outermost marginal ray Lm passing through the surface of the lens element intersects the surface of the lens element. All transition points lie between the optical axis I and the optical boundary OB of the surface of the lens element. If multiple transition points are present on a single surface, then these transition points are sequentially named along the radial direction of the surface with reference numerals starting from the first transition point. For example, the first transition point, e.g., TP1, (closest to the optical axis I), the second transition point, e.g., TP2, (as shown in FIG. 4), and the Nth transition point (farthest from the optical axis I).

The region of a surface of the lens element from the central point to the first transition point TP1 is defined as the optical axis region, which includes the central point. The region located radially outside of the farthest Nth transition point from the optical axis I to the optical boundary OB of the surface of the lens element is defined as the periphery region. In some embodiments, there may be intermediate regions present between the optical axis region and the periphery region, with the number of intermediate regions depending on the number of the transition points.

The shape of a region is convex if a collimated ray being parallel to the optical axis I and passing through the region is bent toward the optical axis I such that the ray intersects the optical axis I on the image side A2 of the lens element. The shape of a region is concave if the extension line of a collimated ray being parallel to the optical axis I and passing through the region intersects the optical axis I on the object side A1 of the lens element.

Additionally, referring to FIG. 1, the lens element 100 may also have a mounting portion 130 extending radially outward from the optical boundary OB. The mounting portion 130 is typically used to physically secure the lens element to a corresponding element of the optical system (not shown). Imaging rays do not reach the mounting portion 130. The structure and shape of the mounting portion 130 are only examples to explain the technologies, and should not be taken as limiting the scope of the present disclosure. The mounting portion 130 of the lens elements discussed below may be partially or completely omitted in the following drawings.

Referring to FIG. 2, optical axis region Z1 is defined between central point CP and first transition point TP1. Periphery region Z2 is defined between TP1 and the optical boundary OB of the surface of the lens element. Collimated ray 211 intersects the optical axis I on the image side A2 of lens element 200 after passing through optical axis region Z1, i.e., the focal point of collimated ray 211 after passing through optical axis region Z1 is on the image side A2 of the lens element 200 at point R in FIG. 2. Accordingly, since the ray itself intersects the optical axis I on the image side A2 of the lens element 200, optical axis region Z1 is convex. On the contrary, collimated ray 212 diverges after passing through periphery region Z2. The extension line EL of collimated ray 212 after passing through periphery region Z2 intersects the optical axis I on the object side A1 of lens element 200, i.e., the focal point of collimated ray 212 after passing through periphery region Z2 is on the object side A1 at point M in FIG. 2. Accordingly, since the extension line EL of the ray intersects the optical axis I on the object side A1 of the lens element 200, periphery region Z2 is concave. In the lens element 200 illustrated in FIG. 2, the first transition point TP1 is the border of the optical axis region and the periphery region, i.e., TP1 is the point at which the shape changes from convex to concave.

Alternatively, there is another way for a person having ordinary skill in the art to determine whether an optical axis region is convex or concave by referring to the sign of “Radius” (the “R” value), which is the paraxial radius of shape of a lens surface in the optical axis region. The R value is commonly used in conventional optical design software such as Zemax and CodeV. The R value usually appears in the lens data sheet in the software. For an object-side surface, a positive R value defines that the optical axis region of the object-side surface is convex, and a negative R value defines that the optical axis region of the object-side surface is concave. Conversely, for an image-side surface, a positive R value defines that the optical axis region of the image-side surface is concave, and a negative R value defines that the optical axis region of the image-side surface is convex. The result found by using this method should be consistent with the method utilizing intersection of the optical axis by rays/extension lines mentioned above, which determines surface shape by referring to whether the focal point of a collimated ray being parallel to the optical axis I is on the object-side or the image-side of a lens element. As used herein, the terms “a shape of a region is convex (concave),” “a region is convex (concave),” and “a convex- (concave-) region,” can be used alternatively.

FIG. 3, FIG. 4 and FIG. 5 illustrate examples of determining the shape of lens element regions and the boundaries of regions under various circumstances, including the optical axis region, the periphery region, and intermediate regions as set forth in the present specification.

FIG. 3 is a radial cross-sectional view of a lens element 300. As illustrated in FIG. 3, only one transition point TP1 appears within the optical boundary OB of the image-side surface 320 of the lens element 300. Optical axis region Z1 and periphery region Z2 of the image-side surface 320 of lens element 300 are illustrated. The R value of the image-side surface 320 is positive (i.e., R≥0). Accordingly, the optical axis region Z1 is concave.

In general, the shape of each region demarcated by the transition point will have an opposite shape to the shape of the adjacent region(s). Accordingly, the transition point will define a transition in shape, changing from concave to convex at the transition point or changing from convex to concave. In FIG. 3, since the shape of the optical axis region Z1 is concave, the shape of the periphery region Z2 will be convex as the shape changes at the transition point TP1.

FIG. 4 is a radial cross-sectional view of a lens element 400. Referring to FIG. 4, a first transition point TP1 and a second transition point TP2 are present on the object-side surface 410 of lens element 400. The optical axis region Z1 of the object-side surface 410 is defined between the optical axis I and the first transition point TP1. The R value of the object-side surface 410 is positive (i.e., R>0). Accordingly, the optical axis region Z1 is convex.

The periphery region Z2 of the object-side surface 410, which is also convex, is defined between the second transition point TP2 and the optical boundary OB of the object-side surface 410 of the lens element 400. Further, intermediate region Z3 of the object-side surface 410, which is concave, is defined between the first transition point TP1 and the second transition point TP2. Referring once again to FIG. 4, the object-side surface 410 includes an optical axis region Z1 located between the optical axis I and the first transition point TP1, an intermediate region Z3 located between the first transition point TP1 and the second transition point TP2, and a periphery region Z2 located between the second transition point TP2 and the optical boundary OB of the object-side surface 410. Since the shape of the optical axis region Z1 is designed to be convex, the shape of the intermediate region Z3 is concave as the shape of the intermediate region Z3 changes at the first transition point TP1, and the shape of the periphery region Z2 is convex as the shape of the periphery region Z2 changes at the second transition point TP2.

FIG. 5 is a radial cross-sectional view of a lens element 500. Lens element 500 has no transition point on the object-side surface 510 of the lens element 500. For a surface of a lens element with no transition point, for example, the object-side surface 510 the lens element 500, the optical axis region Z1 is defined as the region between 0-50% of the distance between the optical axis I and the optical boundary OB of the surface of the lens element and the periphery region is defined as the region between 50%-100% of the distance between the optical axis I and the optical boundary OB of the surface of the lens element. Referring to lens element 500 illustrated in FIG. 5, the optical axis region Z1 of the object-side surface 510 is defined between the optical axis I and 50% of the distance between the optical axis I and the optical boundary OB. The R value of the object-side surface 510 is positive (i.e., R>0). Accordingly, the optical axis region Z1 is convex. For the object-side surface 510 of the lens element 500, because there is no transition point, the periphery region Z2 of the object-side surface 510 is also convex. It should be noted that lens element 500 may have a mounting portion (not shown) extending radially outward from the periphery region Z2.

As shown in FIG. 6, the optical imaging lens 1 of six lens elements of the present invention, located from an object side A1 (where an object is located) to an image side A2 along an optical axis I, is mainly composed of six lens elements, sequentially has an aperture stop 80, a first lens element 10, a second lens element 20, a third lens element 30, a fourth lens element 40, a fifth lens element 50, a sixth lens element 60 and an image plane 91. Generally speaking, the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the sixth lens element 60 may be made of a transparent plastic material but the present invention is not limited to this, and each lens element has an appropriate refracting power. In the present invention, lens elements having refracting power included by the optical imaging lens 1 are only the six lens elements (the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the sixth lens element 60) described above. The optical axis I is the optical axis of the entire optical imaging lens 1, and the optical axis of each of the lens elements coincides with the optical axis of the optical imaging lens 1.

Furthermore, the optical imaging lens 1 includes an aperture stop (ape. stop) 80 disposed in an appropriate position. In FIG. 6, the aperture stop 80 is disposed between the object side A1 and the first lens element 10. When imaging rays emitted or reflected by an object (not shown) which is located at the object side A1 enters the optical imaging lens 1 of the present invention, it forms a clear and sharp image on the image plane 91 at the image side A2 after passing through the aperture stop 80, the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50, the sixth lens element 60, and a filter 90. In one embodiment of the present invention, the filter 90 may be a filter of various suitable functions to filter out light of a specific wavelength, for embodiment, the filter 90 may be an infrared cut filter (infrared cut-off filter), placed between the sixth lens element 60 and the image plane 91 to keep the infrared light in the imaging rays from reaching the image plane 91 to jeopardize the imaging quality.

The first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the sixth lens element 60 of the optical imaging lens 1 each has an object-side surface 11, 21, 31, 41, 51 and 61 facing toward the object side A1 and allowing imaging rays to pass through as well as an image-side surface 12, 22, 32, 42, 52 and 62 facing toward the image side A2 and allowing the imaging rays to pass through. Furthermore, each object-side surface and image-side surface of lens elements in the optical imaging lens of present invention has an optical axis region and a periphery region.

Each lens element in the optical imaging lens 1 of the present invention further has a thickness T along the optical axis I. For embodiment, the first lens element 10 has a first lens element thickness T1, the second lens element 20 has a second lens element thickness T2, the third lens element 30 has a third lens element thickness T3, the fourth lens element 40 has a fourth lens element thickness T4, the fifth lens element 50 has a fifth lens element thickness T5, and the sixth lens element 60 has a sixth lens element thickness T6. Therefore, a sum of thicknesses of all the six lens elements in the optical imaging lens 1 along the optical axis I is ALT=T1+T2+T3+T4+T5+T6. Tmax is the largest thickness of a lens element from the first lens element to the sixth lens element, i.e. the largest thickness of T1, T2, T3, T4, T5, and T6.

In addition, between two adjacent lens elements in the optical imaging lens 1 of the present invention there may be an air gap along the optical axis I. In embodiments, there is an air gap G12 between the first lens element 10 and the second lens element 20, an air gap G23 between the second lens element 20 and the third lens element 30, an air gap G34 between the third lens element 30 and the fourth lens element 40, an air gap G45 between the fourth lens element 40 and the fifth lens element 50 as well as an air gap G56 between the fifth lens element 50 and the sixth lens element 60. Therefore, a sum of five air gaps from the first lens element 10 to the sixth lens element 60 along the optical axis I is AAG=G12+G23+G34+G45+G56. Gmax is the largest air gap from the first lens element to the sixth lens element, i.e. the largest air gap of G12, G23, G34, G45, and G56. Gmax2 is the second largest air gap from the first lens element to the sixth lens element, i.e. the second largest air gap of G12, G23, G34, G45, and G56.

In addition, a distance from the object-side surface 11 of the first lens element 10 to the image plane 91, namely a system length of the optical imaging lens 1 along the optical axis I is TTL; an effective focal length of the optical imaging lens is EFL; a distance from the image-side surface 62 of the sixth lens element 60 to the image plane 91 along the optical axis I is BFL; a distance from the object-side surface 11 of the first lens element 10 to the image-side surface 62 of the sixth lens element 60 along the optical axis I is TL. HFOV stands for the half field of view of the entire optical imaging lens 1. ImgH is an image height of the optical imaging lens 1. Fno is the f-number of the optical imaging lens.

When the filter 90 is placed between the sixth lens element 60 and the image plane 91, an air gap between the sixth lens element 60 and the filter 90 along the optical axis I is G6F; a thickness of the filter 90 along the optical axis I is TF; an air gap between the filter 90 and the image plane 91 along the optical axis I is GFP; and a distance from the image-side surface 62 of the sixth lens element 60 to the image plane 91 along the optical axis I is BFL. Therefore, BFL=G6F+TF+GFP.

Furthermore, a focal length of the first lens element 10 is f1; a focal length of the second lens element 20 is f2; a focal length of the third lens element 30 is f3; a focal length of the fourth lens element 40 is f4; a focal length of the fifth lens element 50 is f5; a focal length of the sixth lens element 60 is f6; a refractive index of the first lens element 10 is n1; a refractive index of the second lens element 20 is n2; a refractive index of the third lens element 30 is n3; a refractive index of the fourth lens element 40 is n4; a refractive index of the fifth lens element 50 is n5; a refractive index of the sixth lens element 60 is n6; an Abbe number of the first lens element 10 is υ1; an Abbe number of the second lens element 20 is υ2; an Abbe number of the third lens element 30 is υ3; and an Abbe number of the fourth lens element 40 is υ4; an Abbe number of the fifth lens element 50 is υ5; and an Abbe number of the sixth lens element 60 is υ6.

First Embodiment

Please refer to FIG. 6 which illustrates the first embodiment of the optical imaging lens 1 of the present invention. Please refer to FIG. 7A for the longitudinal spherical aberration on the image plane 91 of the first embodiment; please refer to FIG. 7B for the field curvature aberration on the sagittal direction; please refer to FIG. 7C for the field curvature aberration on the tangential direction; and please refer to FIG. 7D for the distortion aberration. The Y axis of the spherical aberration in each embodiment is “field of view” for 1.0. The Y axis of the field curvature aberration and the distortion aberration in each embodiment stands for the “image height” (ImgH), which is 5.161 mm.

Only the six lens elements 10, 20, 30, 40, 50 and 60 of the optical imaging lens 1 of the first embodiment have refracting power. The optical imaging lens 1 also has an aperture stop 80, a filter 90, and an image plane 91. The aperture stop 80 is provided between the object side A1 and the first lens element 10. The filter 90 may be an infrared cut-off filter.

The first lens element 10 has positive refracting power. An optical axis region 13 and a periphery region 14 of the object-side surface 11 of the first lens element 10 are convex. An optical axis region 16 and a periphery region 17 of the image-side surface 12 of the first lens element 10 are concave. Besides, both the object-side surface 11 and the image-side surface 12 of the first lens element 10 are aspherical surfaces, but it is not limited thereto.

The second lens element 20 has negative refracting power. An optical axis region 23 and a periphery region 24 of the object-side surface 21 of the second lens element 20 are convex. An optical axis region 26 and a periphery region 27 of the image-side surface 22 of the second lens element 20 are concave. Besides, both the object-side surface 21 and the image-side surface 22 of the second lens element 20 are aspherical surfaces, but it is not limited thereto.

The third lens element 30 has positive refracting power. An optical axis region 33 and a periphery region 34 of the object-side surface 31 of the third lens element 30 are concave. An optical axis region 36 and a periphery region 37 of the image-side surface 32 of the third lens element 30 are convex. Besides, both the object-side surface 31 and the image-side surface 32 of the third lens element 30 are aspherical surfaces, but it is not limited thereto.

The fourth lens element 40 has negative refracting power. An optical axis region 43 of the object-side surface 41 of the fourth lens element 40 is convex and a periphery region 44 of the object-side surface 41 of the fourth lens element 40 is concave. An optical axis region 46 of the image-side surface 42 of the fourth lens element 40 is concave and a periphery region 47 of the image-side surface 42 of the fourth lens element 40 is convex. Besides, both the object-side surface 41 and the image-side surface 42 of the fourth lens element 40 are aspherical surfaces, but it is not limited thereto.

The fifth lens element 50 has positive refracting power. An optical axis region 53 and a periphery region 54 of the object-side surface 51 of the fifth lens element 50 are concave. An optical axis region 56 and a periphery region 57 of the image-side surface 52 of the fifth lens element 50 are convex. Besides, both the object-side surface 51 and the image-side surface 52 of the fifth lens element 50 are aspherical surfaces, but it is not limited thereto.

The sixth lens element 60 has negative refracting power. An optical axis region 63 of the object-side surface 61 of the sixth lens element 60 is concave and a periphery region 64 of the object-side surface 61 of the sixth lens element 60 is convex. An optical axis region 66 of the image-side surface 62 of the sixth lens element 60 is concave and a periphery region 67 of the image-side surface 62 of the sixth lens element 60 is convex. Besides, both the object-side surface 61 and the image-side surface 62 of the sixth lens element 60 are aspherical surfaces, but it is not limited thereto. The filter 90 is disposed between the image-side surface 62 of the sixth lens element 60 and the image plane 91.

In the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the sixth lens element 60 of the optical imaging lens element 1 of the present invention, there are 12 surfaces, such as the object-side surfaces 11/21/31/41/51/61 and the image-side surfaces 12/22/32/42/52/62. If a surface is aspherical, these aspheric coefficients are defined according to the following formula:

${Z(Y)} = {{\frac{Y^{2}}{R}\text{/}\left( {1 + \sqrt{1 - {\left( {1 + K} \right)\frac{Y^{2}}{R^{2}}}}} \right)} + {\sum\limits_{i = 1}^{n}\;{a_{i} \times Y^{i}}}}$

In which:

Y represents a vertical distance from a point on the aspherical surface to the optical axis I; Z represents the depth of an aspherical surface (the perpendicular distance between the point of the aspherical surface at a distance Y from the optical axis I and the tangent plane of the vertex on the optical axis I of the aspherical surface); R represents the curvature radius of the lens element surface; K is a conic constant; and a_(i) is the aspheric coefficient of the i^(th) order.

The optical data of the first embodiment of the optical imaging lens 1 are shown in FIG. 22 while the aspheric surface data are shown in FIG. 23. In the present embodiments of the optical imaging lens, the f-number of the entire optical imaging lens is Fno, EFL is the effective focal length, HFOV stands for the half field of view of the entire optical imaging lens, and the unit for the radius, the thickness and the focal length is in millimeters (mm). In this embodiment, EFL=5.457 mm; HFOV=42.498 degrees; TTL=6.336 mm; Fno=2.580; ImgH=5.161 mm.

Second Embodiment

Please refer to FIG. 8 which illustrates the second embodiment of the optical imaging lens 1 of the present invention. It is noted that from the second embodiment to the following embodiments, in order to simplify the figures, only the components different from what the first embodiment has, and the basic lens elements will be labeled in figures. Other components that are the same as what the first embodiment has, such as a convex surface or a concave surface, are omitted in the following embodiments. Please refer to FIG. 9A for the longitudinal spherical aberration on the image plane 91 of the second embodiment, please refer to FIG. 9B for the field curvature aberration on the sagittal direction, please refer to FIG. 9C for the field curvature aberration on the tangential direction, and please refer to FIG. 9D for the distortion aberration. The components in this embodiment are similar to those in the first embodiment, but the optical data such as the refracting power, the radius, the lens thickness, the aspheric surface or the back focal length in this embodiment are different from the optical data in the first embodiment.

The optical data of the second embodiment of the optical imaging lens are shown in FIG. 24 while the aspheric surface data are shown in FIG. 25. In this embodiment, EFL=5.190 mm; HFOV=42.490 degrees; TTL=6.287 mm; Fno=1.950; ImgH=5.161 mm. In particular, 1) TTL of the optical imaging lens in this embodiment is shorter than that of the optical imaging lens in the first embodiment, 2) the aperture stop of the optical imaging lens in this embodiment is larger than that of the optical imaging lens in the first embodiment.

Third Embodiment

Please refer to FIG. 10 which illustrates the third embodiment of the optical imaging lens 1 of the present invention. Please refer to FIG. 11A for the longitudinal spherical aberration on the image plane 91 of the third embodiment; please refer to FIG. 11B for the field curvature aberration on the sagittal direction; please refer to FIG. 11C for the field curvature aberration on the tangential direction; and please refer to FIG. 11D for the distortion aberration. The components in this embodiment are similar to those in the first embodiment, but the optical data such as the refracting power, the radius, the lens thickness, the aspheric surface or the back focal length in this embodiment are different from the optical data in the first embodiment.

The optical data of the third embodiment of the optical imaging lens are shown in FIG. 26 while the aspheric surface data are shown in FIG. 27. In this embodiment, EFL=5.358 mm; HFOV=41.462 degrees; TTL=6.385 mm; Fno=1.950; ImgH=5.161 mm. In particular, 1) the aperture stop of the optical imaging lens in this embodiment is larger than that of the optical imaging lens in the first embodiment, 2) the field curvature aberration on the tangential direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment.

Fourth Embodiment

Please refer to FIG. 12 which illustrates the fourth embodiment of the optical imaging lens 1 of the present invention. Please refer to FIG. 13A for the longitudinal spherical aberration on the image plane 91 of the fourth embodiment; please refer to FIG. 13B for the field curvature aberration on the sagittal direction; please refer to FIG. 13C for the field curvature aberration on the tangential direction; and please refer to FIG. 13D for the distortion aberration. The components in this embodiment are similar to those in the first embodiment, but the optical data such as the refracting power, the radius, the lens thickness, the aspheric surface or the back focal length in this embodiment are different from the optical data in the first embodiment. Besides, in this embodiment, a periphery region 17 of the image-side surface 12 of the first lens element 10 is convex.

The optical data of the fourth embodiment of the optical imaging lens are shown in FIG. 28 while the aspheric surface data are shown in FIG. 29. In this embodiment, EFL=5.518 mm; HFOV=40.509 degrees; TTL=6.676 mm; Fno=1.950; ImgH=5.161 mm. In particular, 1) the aperture stop of the optical imaging lens in this embodiment is larger than that of the optical imaging lens in the first embodiment, 2) the longitudinal spherical aberration of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 3) the field curvature aberration on the sagittal direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 4) the field curvature aberration on the tangential direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 5) and the thickness difference between the optical axis region and the periphery region in this embodiment is smaller than that of the optical imaging lens in the first embodiment so it is easier to fabricate to have better yield.

Fifth Embodiment

Please refer to FIG. 14 which illustrates the fifth embodiment of the optical imaging lens 1 of the present invention. Please refer to FIG. 15A for the longitudinal spherical aberration on the image plane 91 of the fifth embodiment; please refer to FIG. 15B for the field curvature aberration on the sagittal direction; please refer to FIG. 15C for the field curvature aberration on the tangential direction, and please refer to FIG. 15D for the distortion aberration. The components in this embodiment are similar to those in the first embodiment, but the optical data such as the refracting power, the radius, the lens thickness, the aspheric surface or the back focal length in this embodiment are different from the optical data in the first embodiment. Besides, in this embodiment, a periphery region 17 of the image-side surface 12 of the first lens element 10 is convex.

The optical data of the fifth embodiment of the optical imaging lens are shown in FIG. 30 while the aspheric surface data are shown in FIG. 31. In this embodiment, EFL=5.598 mm; HFOV=38.950 degrees; TTL=6.590 mm; Fno=1.950; ImgH=5.161 mm. In particular, 1) the aperture stop of the optical imaging lens in this embodiment is larger than that of the optical imaging lens in the first embodiment, 2) the longitudinal spherical aberration of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 3) the field curvature aberration on the sagittal direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 4) the field curvature aberration on the tangential direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment.

Sixth Embodiment

Please refer to FIG. 16 which illustrates the sixth embodiment of the optical imaging lens 1 of the present invention. Please refer to FIG. 17A for the longitudinal spherical aberration on the image plane 91 of the sixth embodiment; please refer to FIG. 17B for the field curvature aberration on the sagittal direction; please refer to FIG. 17C for the field curvature aberration on the tangential direction, and please refer to FIG. 17D for the distortion aberration. The components in this embodiment are similar to those in the first embodiment, but the optical data such as the refracting power, the radius, the lens thickness, the aspheric surface or the back focal length in this embodiment are different from the optical data in the first embodiment.

The optical data of the sixth embodiment of the optical imaging lens are shown in FIG. 32 while the aspheric surface data are shown in FIG. 33. In this embodiment, EFL=5.359 mm; HFOV=41.395 degrees; TTL=6.420 mm; Fno=1.950; ImgH=5.161 mm. In particular, 1) the aperture stop of the optical imaging lens in this embodiment is larger than that of the optical imaging lens in the first embodiment, 2) the longitudinal spherical aberration of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 3) the field curvature aberration on the sagittal direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 4) the field curvature aberration on the tangential direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment.

Seventh Embodiment

Please refer to FIG. 18 which illustrates the seventh embodiment of the optical imaging lens 1 of the present invention. Please refer to FIG. 19A for the longitudinal spherical aberration on the image plane 91 of the seventh embodiment; please refer to FIG. 19B for the field curvature aberration on the sagittal direction; please refer to FIG. 19C for the field curvature aberration on the tangential direction, and please refer to FIG. 19D for the distortion aberration. The components in this embodiment are similar to those in the first embodiment, but the optical data such as the refracting power, the radius, the lens thickness, the aspheric surface or the back focal length in this embodiment are different from the optical data in the first embodiment.

The optical data of the seventh embodiment of the optical imaging lens are shown in FIG. 34 while the aspheric surface data are shown in FIG. 35. In this embodiment, EFL=5.112 mm; HFOV=42.123 degrees; TTL=6.239 mm; Fno=1.950; ImgH=5.161 mm. In particular, 1) TTL of the optical imaging lens in this embodiment is shorter than that of the optical imaging lens in the first embodiment, 2) the aperture stop of the optical imaging lens in this embodiment is larger than that of the optical imaging lens in the first embodiment, 3) the longitudinal spherical aberration of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 4) the field curvature aberration on the sagittal direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 5) the field curvature aberration on the tangential direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, and 6) the thickness difference between the optical axis region and the periphery region this embodiment is smaller than that of the optical imaging lens in the first embodiment so it is easier to fabricate to have better yield.

Eighth Embodiment

Please refer to FIG. 20 which illustrates the eighth embodiment of the optical imaging lens 1 of the present invention. Please refer to FIG. 21A for the longitudinal spherical aberration on the image plane 91 of the eighth embodiment; please refer to FIG. 21B for the field curvature aberration on the sagittal direction; please refer to FIG. 21C for the field curvature aberration on the tangential direction, and please refer to FIG. 21D for the distortion aberration. The components in this embodiment are similar to those in the first embodiment, but the optical data such as the refracting power, the radius, the lens thickness, the aspheric surface or the back focal length in this embodiment are different from the optical data in the first embodiment.

The optical data of the eighth embodiment of the optical imaging lens are shown in FIG. 36 while the aspheric surface data are shown in FIG. 37. In this embodiment, EFL=5.560 mm; HFOV=40.838 degrees; TTL=6.603 mm; Fno=1.950; ImgH=5.161 mm. In particular, 1) the aperture stop of the optical imaging lens in this embodiment is larger than that of the optical imaging lens in the first embodiment, 2) the longitudinal spherical aberration of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, 3) the field curvature aberration on the sagittal direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment, and 4) the field curvature aberration on the tangential direction of the optical imaging lens in this embodiment is better than that of the optical imaging lens in the first embodiment.

Some important parameters and ratios in each embodiment are shown in FIG. 38 and in FIG. 39.

The applicant found that in accordance with the following designs, the lens configuration of the present invention has the following features and corresponding advantages:

1. That the first lens element has positive refracting power, an optical axis region of the object-side surface of the second lens element is convex, the third lens element has positive refracting power and an optical axis region of the image-side surface of the third lens element is convex, an optical axis region of the image-side surface of the fifth lens element is convex, ImgH/Fno≥2.000 mm to go with υ2+υ3+υ4+υ6≤135.000 may increase the luminous flux and the image height as well as further improve the chromatic aberration of the optical system. The preferable range of ImgH/Fno is 2.000 mm≤ImgH/Fno≤2.900 mm. The preferable range of υ2+υ3+υ4+υ6 is 105.000≤υ2+υ3+υ4+υ6≤135.000. 2. That an optical axis region of the object-side surface of the second lens element is convex, an optical axis region of the object-side surface of the third lens element is concave, the fourth lens element has negative refracting power, an optical axis region of the object-side surface of the fifth lens element is concave, an optical axis region of the object-side surface of the sixth lens element is concave, ImgH/Fno≥2.000 mm to go with (a) (EFL+ImgH)/(Tmax+Gmax)≥6.000 or (b) a periphery region of the image-side surface of the sixth lens element is convex and (EFL+ImgH)/(Gmax+Gmax2)≥9.300 may increase the luminous flux, increase the image height and keep good imaging quality as well as further improve the aberration and decrease the distortion aberration of the optical system. The preferable range of (EFL+ImgH)/(Tmax+Gmax) is 6.000≤(EFL+ImgH)/(Tmax+Gmax)≤7.700. The preferable range of (EFL+ImgH)/(Gmax+Gmax2) is 9.300≤(EFL+ImgH)/(Gmax+Gmax2)≤14.300. 3. The air gaps between the adjacent lens elements should be decreased or the thickness of each lens element should be appropriately reduced to decrease the TTL and to keep the imaging quality, to facilitate the assembly and to increase the fabrication yield. However, the assembly or the manufacturing difficulty or the imaging quality should be taken into consideration. If the following numerical conditions are selectively satisfied, the optical imaging lens of the present invention may have better optical arrangements: 1) TTL/(G12+G34)≤16.500, and the preferable range is 10.300≤TTL/(G12+G34)≤16.500; 2) (T1+T2+T3)/(G12+G34)≤5.200, and the preferable range is 2.300≤(T1+T2+T3)/(G12+G34)≤5.200; 3) AAG/(G34+T4)≤3.000, and the preferable range is 2.000≤AAG/(G34+T4)≤3.000; 4) (T4+BFL)/(G23+T3+G56)≥1.400, and the preferable range is 1.400≤(T4+BFL)/(G23+T3+G56)≤1.750; 5) T1/T5≤1.000, and the preferable range is 0.550≤T1/T5≤1.000; 6) (T2+G23+G45)/T3≥2.700, and the preferable range is 2.700≤(T2+G23+G45)/T3≤4.500; 7) TTL/(G12+T3)≥11.000, and the preferable range is 11.000≤TTL/(G12+T3)≤17.400; 8) (T4+T6)/G45≤2.200, and the preferable range is 0.960≤(T4+T6)/G45≤2.200; 9) ALT/(G34+T5)≤3.000, and the preferable range is 1.800≤ALT/(G34+T5)≤3.000; 10) (T1+T5+BFL)/AAG≥1.700, and the preferable range is 1.700≤(T1+T5+BFL)/AAG≤2.550; 11) TL/(T3+T4)≥6.000, and the preferable range is 6.000≤TL/(T3+T4)≤9.000; 12) (G12+T2+T5)/(T3+T6)≥1.100, and the preferable range is 1.100≤(G12+T2+T5)/(T3+T6)≤2.800; 13) TTL/T6≥10.500, and the preferable range is 10.500≤TTL/T6≤21.200; 14) (T1+T4)/G56≥2.100, and the preferable range is 2.100≤(T1+T4)/G56≤6.200; 15) ALT/(G23+T3+G56)≥3.000, and the preferable range is 3.000≤ALT/(G23+T3+G56)≤3.800; 16) ImgH/AAG≥2.600, and the preferable range is 2.600≤ImgH/AAG≤3.700; 17) TL/(G45+G56)≥5.000, and the preferable range is 5.000≤TL/(G45+G56)≤8.200.

Any arbitrary combination of the parameters of the embodiments can be selected to increase the lens limitation so as to facilitate the design of the same structure of the present invention.

In the light of the unpredictability of the optical imaging lens, the above conditional formulas preferably suggest the above principles to have a shorter total length of the optical imaging lens, a larger aperture stop, a wider field of view, a greater image height, better imaging quality or a better fabrication yield to overcome the drawbacks of prior art. The lens elements of the present invention are made of a transparent plastic material to decrease the weight of the optical imaging lens and to decrease the cost.

The numeral value ranges within the maximum and minimum values obtained from the combination ratio relationships of the optical parameters disclosed in each embodiment of the invention can all be implemented accordingly.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. An optical imaging lens, from an object side to an image side in order along an optical axis comprising: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element, the first lens element to the sixth lens element each having an object-side surface facing toward the object side and allowing imaging rays to pass through as well as an image-side surface facing toward the image side and allowing the imaging rays to pass through, wherein: the first lens element has positive refracting power; an optical axis region of the object-side surface of the second lens element is convex; the third lens element has positive refracting power and an optical axis region of the image-side surface of the third lens element is convex; and an optical axis region of the image-side surface of the fifth lens element is convex; wherein the optical imaging lens has only six lens elements, ImgH is an image height of the optical imaging lens, Fno is the f-number of the optical imaging lens, υ2 is an Abbe number of the second lens element, υ3 is an Abbe number of the third lens element, υ4 is an Abbe number of the fourth lens element and υ6 is an Abbe number of the sixth lens element to satisfy the relationship: ImgH/Fno≥2.000 mm and υ2+υ3+υ4+υ6≤135.000.
 2. The optical imaging lens of claim 1, wherein TTL is a distance from the object-side surface of the first lens element to an image plane along the optical axis, G12 is an air gap between the first lens element and the second lens element along the optical axis and G34 is an air gap between the third lens element and the fourth lens element along the optical axis, and the optical imaging lens satisfies the relationship: TTL/(G12+G34)≤16.500.
 3. The optical imaging lens of claim 1, wherein T1 is a thickness of the first lens element along the optical axis, T2 is a thickness of the second lens element along the optical axis, T3 is a thickness of the third lens element along the optical axis, G12 is an air gap between the first lens element and the second lens element along the optical axis and G34 is an air gap between the third lens element and the fourth lens element along the optical axis, and the optical imaging lens satisfies the relationship: (T1+T2+T3)/(G12+G34)≤5.200.
 4. The optical imaging lens of claim 1, wherein AAG is a sum of five air gaps from the first lens element to the sixth lens element along the optical axis, T4 is a thickness of the fourth lens element along the optical axis and G34 is an air gap between the third lens element and the fourth lens element along the optical axis, and the optical imaging lens satisfies the relationship: AAG/(G34+T4)≤3.000.
 5. The optical imaging lens of claim 1, wherein BFL is a distance from the image-side surface of the sixth lens element to an image plane along the optical axis, T3 is a thickness of the third lens element along the optical axis, T4 is a thickness of the fourth lens element along the optical axis, G23 is an air gap between the second lens element and the third lens element along the optical axis and G56 is an air gap between the fifth lens element and the sixth lens element along the optical axis, and the optical imaging lens satisfies the relationship: (T4+BFL)/(G23+T3+G56)≥1.400.
 6. The optical imaging lens of claim 1, wherein T1 is a thickness of the first lens element along the optical axis and T5 is a thickness of the fifth lens element along the optical axis, and the optical imaging lens satisfies the relationship: T1/T5≤1.000.
 7. The optical imaging lens of claim 1, wherein T2 is a thickness of the second lens element along the optical axis, T3 is a thickness of the third lens element along the optical axis, G23 is an air gap between the second lens element and the third lens element along the optical axis and G45 is an air gap between the fourth lens element and the fifth lens element along the optical axis, and the optical imaging lens satisfies the relationship: (T2+G23+G45)/T3≥2.700.
 8. An optical imaging lens, from an object side to an image side in order along an optical axis comprising: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element, the first lens element to the sixth lens element each having an object-side surface facing toward the object side and allowing imaging rays to pass through as well as an image-side surface facing toward the image side and allowing the imaging rays to pass through, wherein: an optical axis region of the object-side surface of the second lens element is convex; an optical axis region of the object-side surface of the third lens element is concave; the fourth lens element has negative refracting power; an optical axis region of the object-side surface of the fifth lens element is concave; and an optical axis region of the object-side surface of the sixth lens element is concave; wherein the optical imaging lens has only six lens elements, ImgH is an image height of the optical imaging lens, Fno is the f-number of the optical imaging lens, EFL is an effective focal length of the optical imaging lens, Gmax is the largest air gap from the first lens element to the sixth lens element, Tmax is the largest thickness of a lens element from the first lens element to the sixth lens element to satisfy the relationship: ImgH/Fno≥2.000 mm and (EFL+ImgH)/(Tmax+Gmax)≥6.000.
 9. The optical imaging lens of claim 8, wherein TTL is a distance from the object-side surface of the first lens element to an image plane along the optical axis, T3 is a thickness of the third lens element along the optical axis and G12 is an air gap between the first lens element and the second lens element along the optical axis, and the optical imaging lens satisfies the relationship: TTL/(G12+T3)≥11.000.
 10. The optical imaging lens of claim 8, wherein T4 is a thickness of the fourth lens element along the optical axis, T6 is a thickness of the sixth lens element along the optical axis and G45 is an air gap between the fourth lens element and the fifth lens element along the optical axis, and the optical imaging lens satisfies the relationship: (T4+T6)/G45≤2.200.
 11. The optical imaging lens of claim 8, wherein ALT is a sum of thicknesses of all the six lens elements along the optical axis, T5 is a thickness of the fifth lens element along the optical axis and G34 is an air gap between the third lens element and the fourth lens element along the optical axis, and the optical imaging lens satisfies the relationship: ALT/(G34+T5)≤3.000.
 12. The optical imaging lens of claim 8, wherein AAG is a sum of five air gaps from the first lens element to the sixth lens element along the optical axis, BFL is a distance from the image-side surface of the sixth lens element to an image plane along the optical axis, T1 is a thickness of the first lens element along the optical axis and T5 is a thickness of the fifth lens element along the optical axis, and the optical imaging lens satisfies the relationship: (T1+T5+BFL)/AAG≥1.700.
 13. The optical imaging lens of claim 8, wherein TL is a distance from the object-side surface of the first lens element to the image-side surface of the sixth lens element along the optical axis, T3 is a thickness of the third lens element along the optical axis and T4 is a thickness of the fourth lens element along the optical axis, and the optical imaging lens satisfies the relationship: TL/(T3+T4)≥6.000.
 14. The optical imaging lens of claim 8, wherein T2 is a thickness of the second lens element along the optical axis, T3 is a thickness of the third lens element along the optical axis, T5 is a thickness of the fifth lens element along the optical axis, T6 is a thickness of the sixth lens element along the optical axis and G12 is an air gap between the first lens element and the second lens element along the optical axis, and the optical imaging lens satisfies the relationship: (G12+T2+T5)/(T3+T6)≥1.100.
 15. An optical imaging lens, from an object side to an image side in order along an optical axis comprising: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element, the first lens element to the sixth lens element each having an object-side surface facing toward the object side and allowing imaging rays to pass through as well as an image-side surface facing toward the image side and allowing the imaging rays to pass through, wherein: an optical axis region of the object-side surface of the second lens element is convex; an optical axis region of the object-side surface of the third lens element is concave; the fourth lens element has negative refracting power; an optical axis region of the object-side surface of the fifth lens element is concave; and an optical axis region of the object-side surface of the sixth lens element is concave and a periphery region of the image-side surface of the sixth lens element is convex; wherein the optical imaging lens has only six lens elements, ImgH is an image height of the optical imaging lens, Fno is the f-number of the optical imaging lens, EFL is an effective focal length of the optical imaging lens, Gmax is the largest air gap from the first lens element to the sixth lens element, Gmax2 is the second largest air gap from the first lens element to the sixth lens element to satisfy the relationship: ImgH/Fno≥2.000 mm and (EFL+ImgH)/(Gmax+Gmax2)≥9.300.
 16. The optical imaging lens of claim 15, wherein TTL is a distance from the object-side surface of the first lens element to an image plane along the optical axis and T6 is a thickness of the sixth lens element along the optical axis, and the optical imaging lens satisfies the relationship: TTL/T6≥10.500.
 17. The optical imaging lens of claim 15, wherein T1 is a thickness of the first lens element along the optical axis, T4 is a thickness of the fourth lens element along the optical axis and G56 is an air gap between the fifth lens element and the sixth lens element along the optical axis, and the optical imaging lens satisfies the relationship: (T1+T4)/G56≥2.100.
 18. The optical imaging lens of claim 15, wherein ALT is a sum of thicknesses of all the six lens elements along the optical axis, T3 is a thickness of the third lens element along the optical axis, G23 is an air gap between the second lens element and the third lens element along the optical axis and G56 is an air gap between the fifth lens element and the sixth lens element along the optical axis, and the optical imaging lens satisfies the relationship: ALT/(G23+T3+G56)≥3.000.
 19. The optical imaging lens of claim 15, wherein AAG is a sum of five air gaps from the first lens element to the sixth lens element along the optical axis, and the optical imaging lens satisfies the relationship: ImgH/AAG≥2.600.
 20. The optical imaging lens of claim 15, wherein TL is a distance from the object-side surface of the first lens element to the image-side surface of the sixth lens element along the optical axis, G45 is an air gap between the fourth lens element and the fifth lens element along the optical axis and G56 is an air gap between the fifth lens element and the sixth lens element along the optical axis, and the optical imaging lens satisfies the relationship: TL/(G45+G56)≥5.000. 